Reversal by naloxone of hemorrhagic shock in anephric cats

Hemorrhage, 15 ml/kg induced a rapid fall of blood pressure in intact and anephric cats, but only intact cats demonstrated significant blood pressure recovery following bleeding. Naloxone, 0.1 mg/kg x min, i.v., had a mild promoting effect on blood pressure recovery in the intact cats whereas, in the hemorrhaged anephric cats naloxone re-established an almost complete recovery of blood pressure. These results suggest that endogenous opioid substances play a significant depressor role in hemorrhagic shock, especially in anephric animals.